Summary

In the course of onychomycosis due toTrichophyton mentagrophytes histological studies of nail plate were carried out in order to study growth of the fungus in the nail. The tissue changes caused by assimilation of the nail keratin by the fungus were also studied. Three phases of this process have been described: 1) growth of the fungus in the intercellular spaces, 2) corrosion of nail tissue, 3) gas production. The gas tunnels make an anatomic substratum of the “transverse net” (Alkiewicz 1948) and of the “spriggy net” (Sowiński). The fungus has grown in a monomorphic way in the nail and only arthrospores (spore chains) have been observed.